Function 43h    Read System Status                              (Convertible) 
entry   AH      43h 
return  AL      status bits: 
		0       LCD detached 
		1       reserved 
		2       RS232/parallel powered on 
		3       internal modem powered on 
		4       power activated by alarm 
		5       standby power lost 
		6       external power in use 
		7       battery low